Slicing operations in Go - Step-by-Step Execution

Concept Flow - Slicing operations

Start with an array or slice

↓

Specify slice indices: low:high

↓

Check indices within bounds

Yes↓

Create new slice from original

↓

Use or print the new slice

↓

End

Slicing in Go extracts a portion of an array or slice by specifying start and end indices, creating a new slice referencing the original data.

Execution Sample

Go

package main

import "fmt"

func main() {
    arr := []int{10, 20, 30, 40, 50}
    slice := arr[1:4]
    fmt.Println(slice)
}

Creates a slice from index 1 to 3 of the array and prints it.

Execution Table

Step	Action	Indices	Resulting Slice	Explanation
1	Define array	-	[10 20 30 40 50]	Original array with 5 elements
2	Slice operation	1:4	[20 30 40]	Slice includes elements at indices 1,2,3
3	Print slice	-	[20 30 40]	Output the new slice
4	End	-	-	Slicing complete

💡 Slicing stops after creating and printing the new slice.

Variable Tracker

Variable	Start	After Step 2	Final
arr	[10 20 30 40 50]	[10 20 30 40 50]	[10 20 30 40 50]
slice	nil	[20 30 40]	[20 30 40]

Key Moments - 2 Insights

Why does the slice arr[1:4] include elements at indices 1, 2, and 3 but not 4?

In Go slicing, the start index is inclusive and the end index is exclusive. So arr[1:4] includes elements from index 1 up to but not including index 4, as shown in execution_table row 2.

Does slicing create a new copy of the array elements?

No, slicing creates a new slice header that references the original array's underlying data. Changes to the slice affect the original array, as the slice shares the same data, explained in the concept_flow.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what elements does the slice contain?

A [20 30 40]

B [30 40 50]

C [10 20 30]

D [10 20 30 40]

💡 Hint

Check the 'Resulting Slice' column at step 2 in the execution_table.

At which step is the slice variable assigned a value?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the 'Action' and 'Variable' changes in variable_tracker after step 2.

If we change the slice indices to arr[2:5], what would the resulting slice be?

A [20 30 40]

B [30 40 50]

C [10 20 30]

D [40 50]

💡 Hint

Recall slicing includes start index but excludes end index; check original array values in variable_tracker.

Concept Snapshot

Go slicing syntax: slice := array[low:high]
Includes elements from low (inclusive) to high (exclusive).
Creates a new slice referencing original data.
Indices must be within array bounds.
Useful for extracting parts of arrays or slices.

Full Transcript

This visual execution trace shows how slicing works in Go. We start with an array of integers. Then we create a slice using arr[1:4], which includes elements at indices 1, 2, and 3. The slice does not include the element at index 4 because the end index is exclusive. The slice variable now references this part of the array. When we print the slice, it outputs [20 30 40]. The original array remains unchanged, but the slice shares the same underlying data. This means changes to the slice affect the original array. The trace also clarifies common confusions about inclusive and exclusive indices and the fact that slicing does not copy data but creates a new view. The quiz questions help reinforce understanding by asking about slice contents and variable assignments.